Most videos Ive seen involve pressing buttons rapidly as a method for getting coins easily. It works, but I find actually figuring out the timing on complete accident one day to be a much more effective strategy. I discovered you can time it maybe half a year ago, and now Ive decided to upload a video on my collection of sevens in a single 3,000+ coin run. Now, my first 250+ coins came from what was on the ground, but everything after that mostly came from cherries and sevens (there were other matches of course, but it was mostly those two). This entire video is 13 minutes cut down into a little over two.
Pokemon Fire Red - Proof you can actually time the slot machines